1. Field of the Invention
The present invention relates to a ceramic member support structure for a gas turbine, for supporting ceramic members exposed to a combustion gas.
2. Description of the Related Art
Japanese Patent No. 2717352 discloses a ceramic member support structure of this kind included in a gas turbine, for supporting ceramic members, such as a ceramic scroll for guiding a combustion gas from combustors to a turbine, nozzles (stationary blades) and a turbine rotor, which are superior in heat resisting property to metal members. However, when one of the ceramic members supported by the known ceramic member support structure, such as a scroll, is damaged, the ceramic member support structure becomes incapable of properly supporting the other associated ceramic member, such as the flame tube, and the other associated ceramic member, i.e., the flame tube, is damaged. Thus, damage to one of the ceramic members supported by the ceramic member support structure is likely to affect the rest of the ceramic members.
The present invention has been made in view of the aforesaid problem and it is therefore an object of the present invention to provide a ceramic member support structure for a gas turbine, capable of supporting ceramic members so that the ceramic members may not be easily damaged and damage to one of those ceramic members is scarcely apt to affect other ceramic members.
With the foregoing object in view, a ceramic member support structure according to the present invention for a gas turbine supports a ceramic member by a metallic support member on a housing and connects the ceramic member to the support member so as to be movable relative to the support member by elastic members.
Since the ceramic member support structure for the gas turbine supports the ceramic member by the metallic support member on the housing and connects the ceramic member to the support member so as to be movable relative to the support member by the elastic members, the difference in thermal expansion between the metallic support member and the ceramic member can be absorbed by the elastic members and hence the ceramic member is not damaged easily. Since the ceramic member is supported by the metallic support member, damage to the ceramic member does not affect other ceramic members easily.
Preferably, a metal member is interposed between the adjacent ceramic members arranged along the flowing direction of a combustion gas, respectively.
Since the adjacent ceramic members are not in direct contact with each other, the influence of damage to one of the adjacent ceramic members on the other ceramic member can be suppressed to the least unavoidable extent.
Protrusions may be formed on the outer circumference of the ceramic member and recesses may be formed in the inner circumference of the metallic support member, or protrusions may be formed on the inner circumference of the metallic support member and recesses may be formed in the outer circumference of the ceramic member to combine the ceramic member and the support member in correct positional relation with respect to circumferential and radial directions.
Whereas positioning the ceramic member relative to the support member by means of metal locator pins induces a concentrated stress in the ceramic member, the combination of the protrusions and the recesses is able to position the ceramic member relative to the support member without causing stress concentration.
Preferably, most part of the outer surface of the ceramic member is covered with the support member.
The ceramic member thus covered with the support member do not strike against other members when assembling and disassembling a structure including the ceramic member, so that the possibility of damaging the ceramic member can be reduced.
The ceramic member may be a flame tube included in a combustor, the elastic member may be interposed between an upper end part of the ceramic member and a first support member, and a lower end part of the ceramic member may be pushed in the flowing direction of the combustion gas by the resilience of the elastic member so as to be pressed against a second support member.
The ceramic member, i.e., the flame tube of the combustor, is supported so that the difference in thermal expansion between the flame tube and the metal support member can be absorbed by the elastic member and hence the ceramic member is not damaged easily.
In the ceramic member support structure supporting the flame tube of the combustor, i.e., the ceramic member, an upper end part of a transition duct for carrying a combustion gas from a combustor to a gas turbine may be connected to a lower end part of the second support member by an annular sealing member so as to be movable along a combustion gas passage or in a direction perpendicular to the combustion gas passage relative to the second support member.
Thus, the difference in thermal expansion between the flame tube, i.e., the ceramic member, of the combustor and the second support member of a metal can be absorbed and the gap between a lower end part of the flame tube of the combustor and the upper end part of the transition duct can be surely sealed.
According to the present invention, the ceramic member may be a transition duct for carrying a combustion gas from a combustor to a turbine, an upper end part of the transition duct may be connected through the elastic members to a connecting part of the support member, near an upper end part of the transition duct, and a lower end part of the transition duct may be supported on the housing.
The transition duct, i.e., the ceramic member, can be supported on the housing so that the difference in thermal expansion between the transition duct and the support member of a metal can be absorbed by the elastic member. thus, the transition duct, i.e., the ceramic member, is not damaged easily.
According to the present invention, the plurality of ceramic members may be disposed around the axis of the gas turbine, and a sealing ring consisting of a plurality of segments having the shape of a circular arc may be pressed resiliently against at least the inner or the outer circumferences of the ceramic members.
This ceramic member support structure using the sealing ring consisting of the plurality of segments can be applied to a large gas turbine.